Screening and identification of high selenium-enriched yeast and analysis of aroma-producing substances

Combined with selenium tolerance method and red selenium method, yeasts with high selenium enrichment ability were screened from selenium-enriched soil in Pingli county of Ankang city and Guankou grape samples in Jianshi county. The strains were identified by morphological observation, physiological and biochemical tests and molecular biology techniques. The growth characteristics were studied, and the aroma components in the selenium-enriched fermentation broth of the strain were analyzed by headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results showed that a strain of Torulaspora delbrueckii G-1 with high selenium enrichment ability was screened and identified from soil and grape samples. After being cultured in YPD liquid medium containing Na₂SeO₃ 50 mg/L for 36 h, the selenium contents and biomass were (1.64±0.034) mg/g and (4.80±0.034) g/L, respectively. The strain G-1 could tolerate glucose 200 g/L, SO₂ 300 mg/L and ethanol 6% (V/V). A total of 33 volatile aroma compounds were detected from the fermentation broth of T. delbrueckii G-1, including 8 alcohols, 10 esters, 3 acids, 5 aldehydes and ketones, 3 alkanes and 4 others. Compared with the selenium-free fermentation broth, 17 unique volatile compounds (such as phenylethyl alcohol, ethyl 9-hexadecenoate, nonanoic acid, etc.) were added in the selenium-enriched fermentation broth, which enriched the floral, ester and wax aroma of the fermentation broth.